Chair, in particular work or office chair

ABSTRACT

A chair, in particular a work or office chair, having a backrest rod which can be adjustably tilted with respect to a seat and a backrest displaceable thereon by means of a slider. When tilted back, the slider is slidable with respect to the backrest rod, in a direction of the seat with a displacement device. The backrest is connected with a cradle which is displaceable over a predetermined displacement path and lockable in several positions with respect to the slider. The displacement device has only a single toggle joint seated pivotally around a horizontal pivot shaft on a pillow block supporting the seat or a seat support which is adjustable in inclination towards the pillow block. An extension of the backrest is flexibly connected with a lever end of one lever arm of the toggle joint. Another lever end of another lever arm of the toggle joint is pivotal with a retaining bolt of the backrest rod and the seat support in such a way, that during backward tilting of backrest rod or lowering of the seat support, the one lever arm of the toggle joint displaces the extension and the backrest towards the pillow block or the seat support.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to a chair, in particular a work or office chair,with a backrest frame, the tilt of which can be adjusted relative to theseat and with a backrest support member, displaceable thereon by meansof a slider or the like, where, when tilting back, the slider isslidable in or on the backrest frame in the direction of the seat bymeans of a displacement device.

2. Description of Prior Art

Known chairs of this type offer excellent seating comfort because theyresult in a definite support of the back of the user in the initial orworking position, because of the practically vertical position of thebackrest and they permit relaxed sitting when the backrest frame istilted back. When the backrest frame is tilted back, the upper torso ofthe user does not simply perform a pivot movement, but there is amovement in which several components are superimposed on each other.Because the backrest performs an additional downward movement when thebackrest frame is tilted back, relative movement between the back of theuser and the backrest is avoided or at least reduced to the point whereit is no longer noticeable.

These known chairs have the disadvantage that in the steep initialposition the backrest assumes a defined position relative to the seat,which is adapted to the size of the body of the user. Because thebackrest has an anatomically adapted shape, optimum seating comfort canonly be achieved by a user with an average body size.

SUMMARY OF THE INVENTION

It is the object of the invention to achieve in a chair of the typementioned above that, besides the compensation of the relative movementbetween the body of the user and the backrest during tilting back of thebackrest rod, there is the additional possibility for bringing thebackrest into an initial position which is adapted to the body size ofthe user.

In accordance with the invention this object is attained in that thebackrest is connected with a cradle or the like, which is additionallydisplaceable over a pre-determined displacement path and fixable inseveral positions in or on the slider.

By means of the backrest support member or the like, which isdisplaceable with respect to the slider or the like, without affectingthe displacement path of the slider or the like, which takes placeautomatically via the displacement device, the backrest with thebackrest support member or the like can be brought into an initialposition, which is adapted to the body size of the user, over a separatedisplacement path. In this way the anatomical design of the backresttakes full effect for every user regardless of the body size, which isalso accomplished with relatively minimal additional effort.

Setting of the backrest support member into several definite positionson its displacement path in or on the slider is accomplished in a simplemanner in that a spring with a lock bolt is disposed on the cradle whichcan engage one or a plurality of bores of the slider. The spring can bedisengaged and in this way the locked connection between the lock boltand the slider can be interrupted with a key disposed in the backrestframe.

After the key has been released, the lock position between the lock boltand the slider is automatically assumed if the key is fixed on theslider with an elastic element serving as a restoring spring and, bymeans of extensions, is brought behind the spring in the highestposition of the backrest, and thus of the backrest support member.

In a particularly advantageous embodiment of this invention the springis in the form of a U-shaped leaf spring which laterally encloses thebackrest support member with its lateral arms and is supported by itscross arm on the side of the backrest support member facing the seat onthe side of the slider facing the backrest. The key is disposed on theside of the backrest, frame facing away from the backrest outside of thedisplacement path of the backrest. The key is thus always easilyaccessible and the spring with the lock bolt can be easily housed in thebackrest frame.

The locking force is transferred symmetrically and evenly to the lockbolt if the embodiment is such that the lock bolt is centered on thecross arm of the spring and extends away from it in the direction of theslider, and the row of bores in the slider is centered and placed ateven intervals.

The displacement of the backrest support member in or on the slider islimited by stops, preferably disposed on the slider.

The engagement of the lock bolt in a bore of the slider is improved inthat the free end of the lock bolt terminates in an insertion tip, aninsertion truncated cone shape or the like.

The displacement device for the slider is preferably designed in such away that the displacement device has only a single toggle jointpivotally seated around a pivot shaft on a pillow block supporting theseat or on a seat support which is adjustable in its inclination towardsthe pillow block or seat support. An extension of the slider is flexiblyconnected with the end of one lever arm of the toggle joint and the endof the other lever arm of the toggle joint is pivotal by means of aretaining bolt or the like of the backrest frame and/or the seat supportin such a way, that during backward tilting of the backrest frame and/orlowering of the seat support the one lever arm of the toggle jointdisplaces the extension and thus the backrest in the direction towardsthe pillow block or seat support.

BRIEF DESCRIPTION OF DRAWINGS

The invention will be described in detail by means of an exemplaryembodiment shown in the drawings wherein:

FIG. 1 shows a longitudinal section of the backrest frame with a sliderand a backrest support member bearing the back rest (not shown), as wellas the displacement device for displacing the slider in the backrestframe, and

FIG. 2 shows a partial view of the parts in accordance with FIG. 1, onthe side facing the backrest.

DESCRIPTION OF PREFERRED EMBODIMENTS

The exemplary embodiment in accordance with FIGS. 1 and 2 shows a chairwhere the backrest frame 6 may be pivotally seated on the pillow blockor seat support 33. In this embodiment, the illustration has beenlimited to those parts which are required for placing the backrest intoan initial position and for the automatic displacement of the backrestin or on the backrest frame 6. A displacement device with the togglejoint 20 is shown in FIG. 1, which may be seated either in the fixedpillow block of a chair seat support 33 or in the pillow block or seatsupport 33, which is adjustable in its inclination.

The slider 5 is displaceably guided in the backrest frame 6, dampingelements 7 preventing or damping the noise of backrest displacement. Thesupport member 10 is movably secured to and displaceably guided on theslider 5. The backrest support member 10 supports the horizontal tubesection 9, on which the backrest (not shown) is fixed. Between theslider 5 and the backrest support member 10 the spring 8 in the form ofa U-shaped leaf spring is positioned, which laterally encloses thebackrest support member 10 with its lateral arms and which is supportedwith its cross arm below the backrest support member 10, on the side ofthe slider 5 facing towards the backrest. The slider 5 has a row ofbores 37, as shown in FIG. 2, in its center which are placed at evenintervals. The cross arm of the spring 8 supports on its center the lockbolt 11 which extends away from it in the direction of the slider 5 andterminates on its free end preferably in an insertion tip, an insertiontruncated cone shape or the like, so that it can engage more easily abore 37 of the slider 5.

On the side facing away from the backrest, the key 12 is built into thebackrest frame 6 outside of the displacement area of the backrest, whichcan enclose the backrest frame 6 and take it up in a receiver. Twoextensions of the key 12 rise upward on the sides of the slider 5 andextend behind the spring 8, even when the backrest support member 10 isin its highest position on the slider 5. Therefore, the spring 8 can bedisengaged by pressure on the key 12 and the locked connection betweenthe lock bolt 11 and the slider 5 can be interrupted. Then the backrestsupport member 10 with the backrest can be displaced on the slider 5until the lock bolt 11 again engages a bore 37 of the slider 5, afterthe key 12 has been released. The displacement path of the backrestsupport member 10 on the slider 5 is limited to a predetermined value bycatches of the slider 5, which, for example, may have the form of pinsplaced into the bores. The displacement path of the backrest supportmember 10 on the slider 5 is limited by the backrest support member 10being stopped by the catches. This additional possibility of displacingthe backrest on the slider 5, which itself is automatically displaced inor on the backrest frame 6 in course of the backward tilting of thebackrest frame 6, permits an initial positioning of the backrest whenthe backrest frame 6 steeply extends upward and thus adaptation of theanatomically designed backrest to the body size of the user, so as toattain optimum seating comfort adapted to the body size of the user inall positions of the backrest frame 6.

The key 12 is supported on the slider 5 by means of the elastic element21, which may be in the form of a block of foam material, for example,covered by an adhesive foil 18. This elastic element 21 acts as arestoring spring, which restores the key 12 after it has been released.At the same time the spring 8 is released for engagement of the lockbolt 11 in a bore 37 of the slider 5.

The displacement device for the slider 5 is in the form of a togglejoint 20 in the embodiment shown in the drawings, which is rotatablyseated with the pivot shaft 19 in the form of a seating bolt on thefixed pillow block support 33, or, on the pillow block or seat support33 which is adjustable in its inclination. In such embodiment, theseating bolt is seated in the lateral arms of the pillow block or seatsupport 33. The opening 32 provides space for the toggle joint 20, sothat the structural height can be kept low. The backrest frame 6 is alsoprovided with lateral arms and open towards the backrest. The pillowblock or seat support 33 extends between the lateral arms of thebackrest frame 6 and is rotatably seated in it by means of the pivotshaft 16, in the form of a seating bolt. In the area where they areseated, the pillow block or seat support 33 has the recess 31, throughwhich the extension 17 is brought and flexibly seated on the hinge pin22 by means of the bearing sleeve 24. The hinge pin 22 is disposed atthe end of the one lever arm 28 of the toggle joint 20 which, in theinitial position of the chair, i.e. with the backrest frame 6 extendedsteeply upwards, extends approximately horizontal, the same as thepillow block or seat support 33. In the area of the backrest frame 6which is extended beyond the pivot shaft 16, the retaining bolt 25 isfixed and held in the sliding pad 26. The sliding pad 26 is displaceablyseated in the guide slit 27 of the other lever arm 29 of the togglejoint 20. During pivoting of the toggle joint 20, the hinge pin 22 movesover a track 30 located on a circular path around the pivot shaft 19 ofthe toggle joint 20. The matching of the pivot movement of the backrestframe 6 is such, that the bearing sleeve 24 of the extension 17 movesover a track which coincides with and is identical to the track 30 ofthe hinge pin 22. Thus, the extension 17 can be rigidly connected withthe slider 5 or can be of one piece with it. An appropriate matching canbe provided by the layout of the lever arms 28 and 29 of the togglejoint 20 and of the distance of the hinge pin 22 and the retaining bolt25 from the pivot shaft 19 of the toggle joint 20. The distance of thepivot shafts 16 and 19 on the pillow block or seat support 33 is also aparameter which can be used for definition of the displacement path ofthe slider 5.

In the embodiment shown in the drawings, the extension 17 is a separatepart, which is fixedly connected with the slider 5 by means of theconnecting strip 23, the screw 15 and the spring washer 14. Duringpivoting, the retaining bolt 25 of the backrest frame 6 describes thetrack 36 located on a circular path around the pivot shaft 16. In thecourse of counterclockwise pivoting of the backrest rod 6, the otherlever arm 29 of the toggle joint 20 is pivoted by the retaining bolt 25in the same direction of rotation, as shown in FIG. 1. In this case, thedistance of the retaining pin 25 from the pivot shaft 19 of the togglejoint 20 changes. For this reason, the retaining bolt 25, guided in thesliding pad 26, is guided longitudinally displaceable in the guide slit27 of the other lever arm 29 of the toggle joint 20, in order to performits pivot movement without hindrance on the track 36.

If the toggle joint 20 is pivotally seated on the seat support 33, theretaining bolt 25 is additionally guided adjustably in the guide slitsof the fixed pillow block.

The cover 13 covers a portion of the open side of the backrest frame 6outside of the displacement area of the backrest support member 10.

We claim:
 1. In a chair, in particular a work or office chair, having abackrest frame a tilt of which is adjusted in relation to a seat, abackrest support member displaceable thereon by means of a slider, whentilting back said slider is slidable with respect to said backrest framein a direction of said seat with a displacement device, the improvementcomprising: said backrest support member (10) movably connected to saidslider (5), said backrest support member (10) being displaceable over adisplacement path and lockable in several positions with respect to saidslider (5), said displacement device having only a single toggle joint(20) seated pivotally around a horizontal pivot shaft (19) on one of afixed seat support and a seat support (33) which is adjustable ininclination, an extension (17) of said slider (5) is flexibly connectedwith a lever end of one lever arm (28) of said toggle joint (20), andanother lever end of another lever arm (29) of said toggle joint (20) ispivotal with a retaining bolt (25) of said backrest frame (6) and saidseat support (33) in such a way, that during backward tilting of atleast one of said backrest frame (6) and lowering of said seat supportsaid one lever arm (28) of said toggle joint (20) displaces saidextension (17) and said backrest (35) towards said seat support (33). 2.In a chair according to claim 1, wherein a spring (8) with a lock bolt(11) is positioned on said backrest support member (10), which said lockbolt (11) can engage at least one bore (37) of said slider (5), forminga locked connection, and a key (12) is positioned in said backrest frame(6) which can disengage said spring (8) and said locked connectionbetween said lock bolt (11) and said slider (5).
 3. In a chair accordingto claim 2, wherein said key (12) is supported on said slider (5) bymeans of an elastic element (21) acting as a restoring spring and ispositioned behind said spring (8) with extensions in a highest positionof said backrest support member (10).
 4. In a chair according to claim3, wherein said spring (8) is in a form of a U-shaped leaf spring whichlaterally encloses said backrest support member (10) with lateral armsand which is supported by a cross arm on a backrest support member sideof said backrest support member (10) facing said seat on a slider sideof said slider (5) facing said backrest support member (10), and saidkey (12) is positioned on a backrest frame side of said backrest frame(6) facing away from said backrest support member, outside of adisplacement path of said backrest support member.
 5. In a chairaccording to claim 4, wherein said lock bolt (11) is centered on saidcross arm of said spring (8) and extends away in a direction of saidslider (5), and said slider (5) has a row of bores (37) centered andplaced at even intervals.
 6. In a chair according to claim 1, whereinsaid key (12) is supported on said slider (5) by means of an elasticelement (21) acting as a restoring spring and is positioned behind saidspring (8) with extensions in a highest position of said backrestsupport member (10).
 7. In a chair according to claim 1, wherein saidspring (8) is in a form of a U-shaped leaf spring which laterallyencloses said backrest support member (10) with lateral arms and whichis supported by a cross arm on a backrest support member side of saidbackrest support member (10) facing said seat on a slider side of saidslider (5) facing said backrest support member (10), and said key (12)is positioned on a backrest frame side of said backrest frame (6) facingaway from said backrest support member (10), outside of a displacementpath of said backrest support member (10).
 8. In a chair according toclaim 1, wherein said lock bolt (11) is centered on said cross arm ofsaid spring (8) and extends away in a direction of said slider (5), andsaid slider (5) has a row of bores (37) centered and placed at evenintervals.